The answer is C. We can suppose that the Grey gene is "A" and Black gene is "a". So the gene of heterozygous grey fruit fly is "Aa", and the black-bodied fruit fly is "aa". After mating, the offspring can get only "a" from balck-bodied fruit fly and has equal opportunity to get a "A" or "a" from heterozygous grey fruit fly. If the gene of offspring is "Aa", it will be grey. If "aa", it will be black. So the proportion of being black is 0.5.
It is most likely because Mary’s body went through changes. And from 6 months to a year after pregnancy these “embarrassing symptoms can persist. There can be hormonal changes and cause the body to do abnormal things.
I hope this helps.
What are your answer choices?
The substance is called DNA.
